1. Field of the Invention
The present invention relates to testing apparatuses, more particularly to an apparatus for checking concentricity between the lens barrel and the barrel holder.
2. Description of Related Art
With the ongoing development of microcircuitry and multimedia technology, digital cameras are now in widespread use. High-end portable electronic devices, such as mobile phones and PDAs (Personal Digital Assistants), are being developed to be increasingly multi-functional. Many of these portable electronic devices are now equipped with a digital camera. The camera generally includes an optical module.
Optical modules used for digital camera modules typically include a lens barrel, a lens module, a spacer, a filter, and a lens holder. The lens module, the spacer, and the filter are engagingly received in the lens barrel one on top of one another, in the order written. Generally, the lens barrel is mounted in the lens holder through thread grooves. In an assembly process of the optical module, checking concentricity between the lens barrel and the barrel holder is always needed.
Generally, a method for checking concentricity between the lens barrel and the barrel holder includes following steps: firstly, a light source is disposed at an object side of the optical module and an image sensor is disposed at an image side of the optical module; secondly, light beams emitted from the light source pass through the lens module to form a first spot on the image sensor, meanwhile the position of the spot is recorded; thirdly, the lens barrel is rotated at an angle relative to the lens holder by hand, and a second spot is formed on the image sensor; finally, a distance between the positions of the first spot and the second spot is measured and compared with a predetermined acceptable range to determine whether the concentricity will be accepted.
However, rotating the lens barrel by hand is inefficient and inaccurate due to man-made errors. Thus, the efficiency and precision for checking concentricity are decreased.
What is needed, therefore, is an apparatus for checking concentricity between the lens barrel and the barrel holder with high efficiency and precision.